Distributed computer systems are well known today. For example, a busy web site may employ multiple web servers such as HTTP servers to deliver files in the form of web pages or other type of files. Typically, the multiple web servers are arranged in a pool for load balancing and backup purposes, and are intended to deliver the same files to clients upon their request. In addition, web sites requiring high availability may employ multiple physical locations to guard against failures such as network backbone outages, prolonged power outages, fires, etc. Ideally, the web servers deliver the same files at all times, even when the files are updated, so that all clients receive the same content when making requests at the same time. There are known techniques to enable the web servers to deliver the same content.
One known technique is to provide a single, shared repository for the files, and each web server fetches and delivers the files from this single repository. However, there are problems with this technique—low reliability due to reliance on a single repository, low scalability due to the limited bandwidth and finite response time of a single repository.
Another known technique is for each web server to have its own storage for the files. As the content of a file changes, a server furnishes the changed file to each of the storages. To ensure that each file is updated and made valid at the same time in each of the storages, a known two-phase commit procedure can be used.
An object of the present invention is to distribute new files to different storages of different web servers or other servers, and make them substantially consistent across all of the servers regardless of varying network latency between the source of the new files and the web servers.